Abstract
Abstract The substitution of Si by Al or B in Na2O · 3SiO2 glass has different effects on ionic conductivity. Whereas the activation energy of ionic conduction Eσ, decreases with the amount of Al in sodium aluminosilicate (SAS) glasses, it shows a shallow minimum with respect to B in sodium borosilicate (SBS) glasses. This difference is explained in terms of the strain energy, ΔEs, and bond energy, ΔEb, components of Eσ, which are deduced from recent studies of chemical bonding and local structure of these glasses. It is found that ΔEs increases and ΔEb decreases with increasing Al and B in bond SAS and SBS glasses. The theory of polar covalence has been applied to explain the variation of ΔEb in both glass systems. The dielectric constant is important for evaluating the ionic part of the bond energy, rather than to account for the partially covalent character of the bonds.
Published Version
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